This invention relates to orthopedic devices for limbs and more particularly to a joint assembly for a hip brace that is adjustable to various body shapes while ensuring that the thigh will move from a straight or neutral position wherein extended to an abducted position when flexed to prevent dislocation of the hip joint.
When a hip joint is unstable and subject to subluxation or dislocation, a brace may be employed to stabilize the joint. Such a brace will permit limited movement through the extension/flexion plane while restricting lateral movement i.e. abduction/adduction, or away/toward the midline. Such a brace may be employed for a congenital or injured hip. The most common application of such orthotic devices is after a hip joint has been replaced with an artificial ball and socket joint, especially when the posterior surgical approach is employed. Many of the structures normally holding the ball in place have been cut through. The ball is especially prone to escape from its socket when the leg is flexed and adducted, such as in sitting. To prevent this dislocation, braces applied after hip joint replacement surgery are generally provided with a joint that permits enough flexion extension motion through a limited angle for ambulation and that also provides for a fixed or adjustable degree of abduction. Davis et al. In U.S. Pat. No. 5,421,810 issued Jun. 6, 1995 teach a hinge having a continuously adjustable stop at one end of the extension-flexion rotation. They provide discontinuous means for adjustment of the fixed abduction angle that requires releasing the joint connection, moving the limb to the desired angle, and then tightening the connection. Williamson et al. In U.S. Pat. No 5,368,552 issued Nov. 29, 1994 provide an excellent review of the art and disclose a ball and socket connection in the joint to allow another degree of rotation . Borig et al. In U.S. Pat. No 4,881,532 issued Nov. 21, 1989 disclose ajoint in which there is free abduction through a limited angle.
When fitting a brace, especially a hip brace after surgery, the physician will often prescribe a fixed abduction angle to reduce stress on the joint, especially when sitting. When fabricating the brace, it is difficult to predict what the actual abduction angle will be until it is mounted on the body. If it is not as prescribed, it must be removed, adjusted and mounted again. When the angle is to be changed for some clinical reason, the process must be repeated. When fitting the brace, it is often tempting to disregard small deviations from the required abduction angle. The same holds true for adjustments of the flexion/extension angular extremes.
Diefenbacher and the Applicant, in U.S. patent application Ser. No. 09/148,233 filed Sep. 4, 1998 disclose ajoint with free flexion extension movement between adjustable stops and continuous adjustment of a fixed abduction angle in which the adjustment of abduction angle can be made while the brace is in place on the body.
The joint assemblies of the prior art effectively protect the joint from dislocation when sitting. However, they cause the wearer to stand and walk with the leg abducted. This is uncomfortable and places undue stress on leg structures, and the back. It would be useful to have a brace that would ensure abduction when sitting while providing a leg position when standing and walking that places the foot beneath the hip in a more normal stance.